This invention relates generally to a bellows pump dispenser, and more particularly to such a dispenser in which the bellows is utilized to seal the container vent opening closed in a locked down position of the plunger during non-use conditions such as shipping and storage.
Pump dispensers having a tubular resilient bellows defining a pump cheer located within a pair of relatively reciprocable parts of a pump housing, are known. Such prior art dispensers are normally provided with a valve controlled container vent opening for replacing product dispensed from the container with air to avoid container collapse during dispensing and to aid in priming the bellows pump cheer. The container vent valve, normally one-way, may comprise a resilient lip or flap valve responding to a differential pressure for opening the vent to admit air into container as the pressure within the container drops below atmospheric. However, problems may arise during non-use conditions such as shipping and storage of the dispenser package as product tends to leak through the open container vent during pressure fluctuations acting on opposite sides of the container vent valve. Moreover, should the pump plunger be accidentally depressed during shipping and handling, product is likely to leak through the discharge passage.
The need therefore arises for locking the plunger against reciprocation during periods of non-use, and for sealing the container vent closed during the plunger lock condition.